Green Screen Tips & Tricks – Part 3: Keying with editing programs

So, you have your green screen footage captured…now what?

For starters, you need an editing program in order to key, though that should be obvious. I use the Adobe CC suite, and key in either Premiere or After Effects. It tend to use the Ultra Key in Premiere most often, though Keylight in After Effects is no slouch. The entire Adobe CC suite is available with a monthly paid subscription and can also be used for free as a 30 day trial. If you’re a student or teacher, you can get it as cheap as $19.99/mo which is a bargain.

If you are truly on a shoe-string budget, there are freeware editing programs out there as well as some that are very inexpensive. Though I have not tried them, both Wax and Jahshaka look fairly robust, especially considering the price (free!) and are capable of keying. Whatever your software used for keying, the basic premise remains the same. Using a color selector, you will sample a 1-5 pixel section of the video and all areas containing the same color (or similar – this is controllable) will be rendered transparent and anything placed beneath the video on the timeline will become visible through the transparent areas. Now, if only it were that simple.

This is where Green Screen Tips & Tricks Parts 1 & 2 really come into play. If you had a good color and material for your background and lit it evenly, then you will have very little additional work to do after selecting the color to key out. However, you will inevitably need to tweak the key to get it perfect.

I will cover some of the main points based off of keying in Premiere (using Ultra Key), as that is what I am most familiar with, though Keylight in After Effects works very similarly, though a few of the settings carry different names.

An Opacity mask was applied to this clip with key frames to help track movement prior to applying the Ultra Key.

An Opacity mask was applied to this clip with key frames to help track movement prior to applying the Ultra Key.

First, apply the Ultra Key effect by dragging it from the Effects panel over to the clip in the timeline or onto the Effect Controls if you have the clip already selected. Then, using the eyedropper, select an area of the clip which is the closest to the midtone of the the color you are keying out. I typically find that slightly towards the shadowed/darker side of the keying area is better than a brighter area and will result in less issues as you adjust the key.

ultra key

Once you have done this, clip on the drop down menu above the eyedropper that says Composite. Move down and select the option Alpha Channel. This will allow you to see the clip as a negative and make cleaning up the key much easier. With the clip in Alpha Channel, areas that are black will be transparent and areas that are white will be opaque. You’ll want to make settings adjustments to the Ultra Key in order to get it perfect, and you will need to scrub the timeline in order to be certain that it is clean throughout the entire clip. If any white shows in areas that should be black (transparent) or any black shows in areas that should be white (opaque) then begin to make adjustments to the settings.

alpha channel

The first place I go to make adjustments is the pedestal. I will usually bring this up to anywhere between 65-100. This is the quickest way to reduce excess image noise created by opaque (white) areas that need to be transparent (black). The effects of this change are always immediate, and you will notice a significant improvement in the key, assuming you color selected from a darker mid-tone of the green screen. If more correction is needed, I tend to adjust the Contrast followed by the Mid Point. Usually this gets even a difficult clip to the point that minor adjustments to the Highlight and Shadow will fix any remaining issues. Occasionally, very minor adjustments to the Transparency setting will yield good results, but it is usually best not to go much below 38.

ultra key cu

Once satisfied, go back up and change from Alpha Channel back to Composite and see the results.

finished composite

Lastly, a quick word about color correction. Ultra Key, more so than Keylight, tends to desaturate the color. Adjustments can be made within Ultra Key to the saturation, as well as hue and luminance. This can be particularly useful for compositing, however color correction effects placed beneath the Ultra Key effect on the Effect Control panel, such as RGB Curves, will allow you to make corrections to the color without effecting the key. Contrary to this, placing color correction effects ABOVE the Ultra Key in the Effect Control panel will directly affect the key. This can be used to your benefit, often on particularly difficult clips, allowing you to make changes, with RGB Curves for example, and see an immediate impact on the key. Increasing or decreasing the greens and reds with curves often yields good results.

Don’t be afraid to make adjustments to the settings. If things go horribly wrong, click the reset arrow on the far right of the setting or effect and start over. The more you play with the settings, the better you will become at making a really clean key – fast!

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Something You Should Know Before Watching Star Wars: Episode VII

With the upcoming release of Star Wars Episode VII, I’d like to reflect on the previous installments and in particular, the often criticized Episodes I-III. While there was much to dislike about them (Jar Jar and over convoluted politics aside) there were a few eloquent and overlooked story threads that are worth considering. While many of these have been discussed in part in the past, some still chalk it up to simple “fan theory” as if to imply that George Lucas is somehow incapable of having any possible depth to the characters or story he created. We are, of course, talking about a franchise that has grossed over 27 billion and possibly counts it’s fans in the billions as well.

Let’s start with the concept of the midi-chlorians and the birth of Anakin. In Episode I, The Phantom Menace, when Shmi Skywalker was asked by Qui-Gon Jinn who the father was, she replied:

shmi and qui-gon

There was no father. I carried him, I gave birth, I raised him. I can’t explain what happened.”

I remember this idea of a “virgin birth” left a bad taste in many movie-goers mouths long after the film had left theaters, as the truth behind it was not revealed until Episode III when Palpatine tells Anakin the tale of Darth Plagueis:

create life

Darth Plagueis was a Dark Lord of the Sith, so powerful and so wise he could use the Force to influence the midi-chlorians to create life…

In the scene, as Palpatine is telling Anakin of this, he slows and pauses for a beat, looking at Anakin as he says “create life” – emphasizing, for the audiences’ sake, that this is in reference to Anakin’s birth and actor Ian McDiarmid was no doubt directed to do so by the films director, aka, George Lucas. Repetition, a story telling tool, is used to bring the viewer’s mind back to the first time the term midi-chlorians was used waaaay back in Episode I with regards to Qui-Gon’s search for the origin of Anakin.

However, this key scene from Episode III does not stop with just explaining Anakin’s past – it also eludes to his future. Palpatine immediately follows with:

from dying

He had such a knowledge of the dark side that he could even keep the ones he cared about from dying.

You can watch the entire scene here: https://www.youtube.com/watch?v=HLfGh2b_me0

This is where it begins to get really interesting. This was the impetus that ultimately drove Anakin to the dark side in order to try to save the life of Padmé. Near the end of Episode III, Anakin meets with Padmé only to discover that she is with Obi-Wan and no longer trusts the man Anakin has become. In his anger, Anakin does the first of many of his signature “force choke”. Padme falls and the fight between Anakin and Obi-Wan ensues, and by the end of which, Anakin is severely burned and left to die.

Palpatine shows up and brings Anakin to a medical facility where he is pieced back together in Frankenstein-like fashion in between scenes of Padmé dying on the ship of “unknown” causes. While some have theorized that this was the work of Palpatine taking the life force from Padmé and channeling it into Anakin, I believe it to be something far more tragic.

anakin becomes vader padme dies

What if Darth Vader’s “force choke” is not actually a choke, but a life-force siphon? If this is a power of the self-serving dark side, then would it not make sense that the only life it could ever truly save is that of the Sith using it? That would in turn mean that Anakin, in completely succumbing to the dark side, discovered how to save a life and in his rage used that discovery to draw the life out of the very person he had hoped to save.

Anakin siphons Padme's life force

And so, in almost typical tragic Shakespearean style, Anakin killed Padmé using the very method he hoped to use to save her.

Green Screen Tips & Tricks: Incorporating keyed footage

As a little break between green screen how-to’s, I thought I’d share a couple films I created that give you an idea of ways in which you can incorporate green screen footage. The first, Come Play With Me,  won a Silver Remi at the 2015 Worldfest Houston International Film Festival.

The green screen footage was employed to allow the character to be shrunk on screen and be placed over a series of stop-motion stills. This entire film was written, shot and edited all within the course of a couple days, and almost entirely by myself. The green screening was accomplished in the same small living room that is pictured in the film. I point this out to show you what can be accomplished with limited time and resources. All it takes is a little know how and drive.

This second short film, A Perfect Circle, was created as part of the 2015 Zone Film Race. Teams are given a line of dialogue, a character and 7 days to creat a short sci-fi film. My entry, again created with just a few people, took 4th place overall and won Best Costumes and Best Visual FX.

This film uses almost entirely green screened footage. The composited backgrounds were all created in 3D during the 7 days of film making by myself and three other 3d artists. While creating your entire environment can be somewhat time consuming, it gives you the ability to match all your camera shots perfectly to your footage, as well as your lighting. Not to mention, it makes location scouting and set building a breeze!

Green Screen Tips & Tricks – Part 2: Lighting

The background is now ready set, your cast is in color appropriate wardrobe but it’s not quite time to roll camera. Like any set your ‘green’ screen needs lit, though unlike a normal set, you can’t get away with much less than ideal lighting.

The light on the background, in this case the green screen, needs to be as even as possible. When setting your lights, the aim is to reduce shadows and remove hot spots on the screen. Hot spots occur when an area of the screen is receiving a greater concentration of light than another area. Shadows most often occur when the actor or subject throws a shadow on the background due to one or more of the lights. Will there be much movement by the actors? If so, do a walk through before hand to look for potential issues of strong shadows.

Having even lighting not only makes keying easier, it allows you to key even when there are similar color ranges you don't want to lose.

Having even lighting not only makes keying easier, it allows you to key even when there are similar color ranges you don’t want to lose such as the painted faces in this shot.

even lighting 2

A clean key. Luma was greatly reduced for compositing into the scene.

Being able to adjust the intensity of individual lights helps to reduce hot spots and shadows, as does diffusing the light with frosted gels, softbox lights, white cloth or even layers of white tissue paper. Of course, the biggest contributor to reducing hot spots and shadows is light placement.

softbox lights

I typically use a 4-5 light set up. When using 4 lights, I have 2 to either side of the screen near to the screen itself and heavily diffused. These back lights are angled so that they not only evenly light the screen, but also provide a back/rim light to help separate the subject from the background. The idea is that outside of a few inches at the green screen edge that are hot, the remainder of the screen is evenly lit. The other 2 lights are placed much farther back from the screen, with the primary/Key running the hottest and the secondary/Fill as a fill for the subjects shadowed side. These lights need to be angled so that they do not throw shadows directly behind the subject. The shadows that are cast should fall to the left or right of the subject whenever possible and should not be too harsh. The fifth light, when used, is a top down light from above and slightly behind the subject works as a hair light, though I typically only use this if the scene the characters are going into would have light falling on them from above.

Just as important as attempting to match the lighting of the scene the subject will be placed into, is keeping the lighting even. However, this is not always possible. When keying, I have typically found in post that it is easier to key out slight to moderate shadows than it is to remove highlights (hot spots). Also, when in post, opacity masks or garbage mattes can help to remove trouble areas from your key (more on this in future posts).

Hot spots in the bottom of frame and heavy shadows throughout make this a difficult key, not possible without heavy masking.

Hot spots in the bottom of frame and heavy shadows throughout make this a difficult key, not possible without heavy masking.

This keyframed mask makes the area needed to key much less.

This keyframed mask makes the area needed to key much less.

And lastly, on the subject of lighting, have a shot list and preferably a storyboard as well. To keep consistent light from scene to scene, it can be very difficult to maintain the direction, for example, the sun is coming from if you do not have the storyboard to help you keep that consistent. The shot list means you don’t have to necessarily make more than a few changes to your lighting, by keeping similarly lite shots grouped on the shot list.

Remember, you don’t have to have the most expensive lights, particularly when it comes to your screen back lights. The main thing where they are concerned is giving an even light. Color temperature is not paramount with the back/screen lights. I use a pair of $20 work lights with layers of white tissue paper for my screen lights, and reserve my LED’s for lighting the subject.

Green Screen Tips & Tricks – Part 1: Background

Long before post, before the camera and lighting get set, the background color concerns must be addressed if you wish to capture good, easy to key ‘green’ screen footage.

To begin with, select your keying material and color. Chroma green is the most common, but not the only option, depending on what you will be filming and keying. I once had to use a hot pink color for a book trailer shoot in which I was filming America’s National Parks: A Pop-Up Book with ‘hands-free’ page turning. For obvious reasons green was right out, and blue would have been equally troublesome. The hot pink, which would have been terrible as a keying color for a Caucasian subject (due to their flesh tones), worked wonderfully for the book with few difficulties. Whatever you decide to use for your background, make sure it is smooth and wrinkle-free, non-reflective and not textured. While any color can be keyed out, it is best to use a color that will not be found on your subject(s), be they actor or object.

That brings us to the next part – wardrobe considerations. For obvious reasons, you don’t want your actors wearing a color the same or similar to the background keying color. For example, bright yellow and chroma green are similar enough in color that without perfect lighting this can cause issues.

Notice how the horizon is visible through the yellow shirt of the figure running on the right.
Notice how the horizon is visible through the yellow shirt of the figure running on the right.
Bright yellow on a chroma green screen keys similar to a 'hot spot' on the background.
Bright yellow on a chroma green screen keys similar to a ‘hot spot’ on the background.

You need to be careful of white, as it can pick up color spill from the background and result in fuzzy edges on your keyed subjects. And, of course, stay away from clear and reflective objects, such as glasses or a shiny metal sword, as these will also pick up the green of the background and make keying very difficult, though still not impossible (more on this in future blogs).